1. Field of the Invention
This invention relates to a novel liquid crystal substance and a liquid crystal composition containing the same, and more particularly it relates to a chiral liquid crystal substance having an optically active group and a chiral liquid crystal composition containing the same.
2. Description of the Prior Art
Among liquid crystal display elements, those of twisted nematic (TN) type display mode have currently been most widely used, but they are inferior in response rate to emissive type display elements (e.g. electroluminescence, plasma display, etc.), and various improvements in this respect have been attempted, but it appears, nevertheless, that possibility of notable improvement has not been left behind so much. Thus, various liquid crystal display devices based on a different principle from that of TN type display elements have been tried in place thereof. Among these devices, there is a device of display mode utilizing ferroelectric liquid crystals (N. A. Clark et al, Applied Phys. lett., 36, 899 (1980)). This mode utilizes the chiral smectic C phase (hereinafter abbreviated to S.sub.C * phase), the chiral smectic H phase (hereinafter abbreviated to S.sub.H * phase) or the like of ferroelectric liquid crystals, and substances having such phases in the vicinity of room temperature have been desired as those suitable to this mode.
The present inventors have previously found some chiral smectic liquid crystal compounds suitable to such object and applied for patent (e.g. Japanese patent application Nos. Sho 58-640/1983, Sho 58-78594/1983, Sho 58-119,590/1983, etc.).
The present inventors have further made extensive research on liquid crystal substances having an optically active group in order to find superior compounds suitable to the above display mode, and as a result have found compounds of the present invention.